Video-frequency signal-translating apparatus



oc.. 14, .195s

B. D. LOUGHLIN VIDO-FREQUENCY SIGNAL-TRANSLATING APPARATUS Filed Feb.. ll, 1955 5 Sheets-Sham. 1

oct. V14,1958

B. D. LOUGHLIN VIDEO-FREQUENCY SIGNALATRANSLATING APPARATUS Filed Feb. "1, 1955 I s ,Sheets-sheet 2 Time-v FIGQla FIG..lb

FR OM AMPLIFIER i TO MODULATOR 23 AND SYNCHRONOU S DETECTOR 'To FILTER NETyJIoRK TO PHASE ADJUSTING CIRCUIT 32 GENERATOR TO AMPLIFIER 29 AND PHASE ADJUSTING CIRCUITS 30 AND 33 Oct. 14, 1958 B. D. LoUGHLlN VIDEO-FREQUENCY SIGNAL-TRANSLATING APPARATUS Filed Feb. 11, 1955 5 Sheets-Sheet 3 RH 3 EU ll'mwm G o Am l l l l l l l llfrll C. M l llll Ilclu lllll D l v U M mo om .m Ns 2 W YNT A AU ..Il- 0C G o 4|T MR 5 W3 3 E Il' E R 39 2N OFN OwTz 0 Tu 2 0 TN M Umb Rm IL. Y L MAE 00C 9 TU2 A OF AN D 3| LY cR O US LE M MUMv wv.. N Nrn PwA MM Mmm v om MSM TC U A R R H L OU 6 LLC l IU 8 A w a o Y AE A LW .IAI.. lo o o o q E R G C d- C o M NW DMI NMT G. B HU N0 W a* ENA P. E n. ASC OM L GR R C P 1E A WN... EMM HSN Y DC SHA Dn S M A u 1\ 8 N 3 2 2 Omo Ill lllllllllllllllllllllllll l.. E i @MNE GW MNU 3 OENA O EO RWNWB RUS Fl-AN3 FQ C F SE R G F TO GOLORSWITCHING GRID l4b FIGA United States Patent O VIDEO-FREQUENCY SIGNAL-TRANSLATING i APPARATUS Bernard D. Loughlin, Lynbrook, N. Y., assigner to Hazeltine Research, Inc., Chicago, Ill., a corporation of Illinois Application February 11, 1955, Serial No. 487,567

17 Claims. (Cl. 178-5.4)

General The present invention is directed to video-frequency signal-translating apparatus for a compatible image-reproducing system particularly for use in color-television receivers and, more specifically, to such apparatus for use in a. compatible color-television receiver of the NTSC type utilizing a single-gun type of picture tube in which the electron beam is sequentially directed onto different color phosphors.

In a form of color-television system more completely discussed in many articles in the January, 1954 issue of the Proceedings of the I. R. E., information representative f a scene in color being televised is utilized to develop at the transmitter two substantially simultaneous signals, one of which is primarily representative of the brightness or luminance and the other of which is `representative of the chrominance of the televised image. The latter signal is a subcarrier wave signal having a mean frequency within the video-frequency pass band and having successive cvcles thereof modulated in amplitude at differ-emphases by signal components representative of specific hues of the televised image. The `composite video-frequency signal comprising the luminance signal and the modulated subcarrier wave or chrominance signal is then employed in a conventional manner to modulate a radio-frequency wave signal. The signals just described are utilized in an NTSC type of system and, therefore, will be referred to hereinafter as NTSC type signals.

A receiver in an NTSC type of system intercepts the radiated signal and derives the composite video-frequency signal, including the luminance and chrominance signals, therefrom. One type of such receiver includes a pair of principal channels for individually translating the luminance and chrominance information for application to an image-reproducing device in such receiver. The channel for translating the luminance signal is substantially the same as the video-frequency amplifier stages of a conventional monochrome receiver. In one type of receiver, the channel for translating the chrominance signal includes means for deriving signals representative of the primary colors red, green, and blue and for combining such derived signals with the luminance Signal to provide'signals which may be utilized in an image-reproducing device to effec color reproduction of the televised image. i

More recently, a one-gun type of image-reproducing device, referred to as a focus-mask type of device, and circuits for modifying the NTSC type ofcomposite videofrequency signal for use in such device have been described in an article entitled Processing of the NTSC Color Signal for One-Gun Sequential Color Displays in the January, 1954 issue of the Proceedings of the l. R. E. at pages 299-308, inclusive.` As described in such article, the focus-mask type of picture tube includes repeating groups of parallel strips of different phosphors individually for emitting green, red, and blue colors, each group having the sequence green, red, green, blue. `A grid structure comprising a plurality of conductors which are parallel` to each other and to the phosphor strips on the screen has one of such conductors positioned behind each of the ICC phosphor strips for emitting red and blue colors and none behind the strip for emitting green.

translates information of the color emitted by the excitedL strip. As described inthe I. R. E. article, an NTSC type ,of signal may not be applied directly to a picture tube of the type just described if fidelity of color reproduction is to be obtained. Prior to application to such picture" tube, the luminance signal should be modied to include" a luminance-correction component and the modulated subcarrier wave signal-should be converted into one wave signal of the same mean frequency as the detected chrominance signal and including only color information representative of red and blue'and into a secondharmonic wave signal including information representative of green. The modified luminance signal and fundamental and second harmonic subcarrier wave signals are combined for application to such picture tube to eiiect reproduction of the color image.

Such modified NTSC type of composite video-frequency signal is adequate to reproduce a color image in such picture tube when color information is being transmitted and received. However, when only monochrome information is being received or it is desired to reproduce a monochromeirnage from color signals, the black-andwhite image reproduced in this type of picture tube tends to have spurious color patterns having red and blue, elements. These spurious patterns apparently arise from a heterodyningof the high-frequency monochrome signals, particularlythose signals in the range of 3-4 megacycles, with the color-switching operation occurring at approximately 3.6 megacycles. Such heterodyning results in lowfrequency beat signals of approximately 0-.06 megacycle which appear with high Visibility as red and blue patterns. These spurious effects have been reduced by including in the luminance channel a filter network having an upper cutoff frequency of approximately 3 megacycles so that effectively no luminance information above 3 megacycles is utilized. However, the use of such filter network` is detrimental in preventing the reproduction of high-delinition monochrome images. Though it is desirable to eliminate or minimize the spurious color patterns reproduced in a monochrome image, it is equally important to utilize all of the luminance information available in order to obtain the highest quality of reproduction `and the maximum degree of compatibility. The improved videofrequency signal-translating apparatus for a compatible image-reproducing system in accordance with the present invention is designed to effect such result.

It is, therefore, an object of the present invention to provide a new and improvedvideofrequency signal-translating apparatus for a compatible image-reproducing system by means of which the deficiencies of prior such systems when utilizing an NTSC signal are diminished.

It is another yobject of the present invention to provide a new and improved video-frequency signal-translating apparatus for a color-television receiver including a single-gun type of picture tube which effects increased definition in the reproduced monochrome images.

It is a still further object of the present invention to provide a new and improved video-frequency signaltranslating apparatus for a compatible image-reproducing system for a color-television receiver including a singlegun type of picture tube, and in which the NTSCtype of signal is employed, by means of which reproduced mono- Patented Oct. 14, 1958 Such grid is energized by a signal `synchronized, with the modulated sub-- rsnrqducinaa .monochrome or color image by Peridic.`

linszpf diierehnprimary wlorelementsandus- @to spurious.` color distortigns. during the` repre,-

frequency yideo componentsupon their applica tion to Ql..r,r,1.e 11t;..0f@einen 4primo. olQr.. video-frequency sig al-translating apparatus comprisesa circuit for suplngnchreme .,Or.. 691er Signals.. sghalrgeneratnameas for. developing. a, referentie, Signal. harmencally related'in ivreguencyvto the sampling rate of elements of the given plgrandhaving different phases. with. respecttQ the s anipling'timesof the Agiven color when c olor and'v monoimages are bein `g rep roduced. Finally, thesignslating apparatus includes signal-translating meanscoupled tothesignal-generating means ,and having ayarying,signal-translation factor controlled by the referencesignal and coupled to the supplycircuit for effecting translation A. `of -the supplied highfrequency components primarily at the sampling timesofthe given color when a color i rn age is being reproducedand primarily at other times fwhen a monochrome image is being reproduced. Eorja better understanding of the present invention, together with other and further objects thereof, reference i s l 1 ad. t o the following description taken in connection the accompanying drawings-, and its scope will be pointed out in the appended claims.

Referring to the drawings:

fecei rincluding video-frequency signal-translating a tus fora compatible image-reproducing system in accordance with thepresent invention; Fig, la is a vector ydiagram,useful in explaining the `operationof. the receiver of Fig. 1;

i Fig'. 1b' .co' m'prises a set of curves useful in explaining the operation of the receiver of Fig. 1;v

2 a detailed circuit diagram of the videofrequencyl signal-translating apparatus of Fig.. l1;

Fig. 3 .is a schematic diagram of amodified form of tIhevide'o-frequency signal-translating apparatus of Fig.

. arid v u f Fig. 4is1aschernaticdiagram of another modified form of; the video-frequency signal-translating apparatus of Pfg'. 1.

General description of receiver of Fig. I `vReferring now to Fig. 1 of the drawings, there is represented a color-televisionreceiver of the vsuperiilriua at; least .fliehen-frequency. components f .the

ratus fully considered in the last-mentioned I. R. E. article. The apparatus 14 includes a picture tube having an image screen 14a, a color-switching grid 14b, and horizontal and -vertical defiecti-on windings 14o. Phosphors for emitting green, red, and blue lights are interleaved on the screen 14min the order of green, red, green, and blue with a wire of one group of grid wires of theV grid 14b positioned lbehind eachof the red phosphors and a wire of thel other group behind each blue There is alsot coupledwbetweenthe afQrmentioned output circuit of the source 10 and an input circuit' of the adder circuit 1 3, in cascade in the order named, an amplifier 19 having a'pass hand o'f' approximately 3.0-4.2 megacycles, a video-frequencysignal-translating apparatus 12 in accordance with the present invention and to be considered more fully hereinafter, and a 3.0-4.2 megacycle filter network ,2LH Though the apparatus 12 willbe described fully hereinafter, some of the components of it cooperate with apparatus not in the apparatus 12 and a brief description of these components new g'iven for clarity. For effecting control' of the signal-detecting and color-switching signals to be c'on- F'g. 1y is a. schematic diagram. of a color-te'levision` sidered more fully hereinafter, the apparatus 12 includes,- in cascade in the order named and coupled to an output circuit of the amplifier 19, an automatic-phase-control system 2 7 and a reference-signal generator 28. The generator-Z'S can be a conventional sine-wave generator and the system 27 maintains the operation of the generator 28in synchronism and at a specific phase with respect to a reference signal developed at the transmitter. A more detailed description of the system 27 will be presented hereinafter when considering the apparatus 12 in detail. The loutput circuit ofthe generator 28 is coupled through a push-pull amplifier 29 to the color-switching control grid 14b in the image-reproducing apparatus' 1 4.

There are also coupled, in cascade in the order named, between the aforementioned output circuit of the amplifier 19 andan input circuit of the adder circuit 13, a' G-M axis selector 22, a modulator 23', and a 6.6-7;8 megacycle filter network 24. The output circuit of the generator 28 is coupled through a second harmonic amplier 34, which is a component of the apparatus 12,

heterodyne type suitable for utilizing an NTSC type of color-televisionsignal and, more specifically, a receiver of the .type described in the aforementioned I. R. E. articleentitled-Processing of the NTSC Color Signal for One-Gun Sequential Color Displays. The receiver includes a-video-frequenc'y signal source 10. The source 10 can be conventional equipment for supplyin'gan NTSC type of composite video-frequency signal, for e.- ample, it c`an linclude a radio-frequency amplifier having an'input circuit coupled to an antenna 11, an oscillatormodulator, an-intermediate-frequency amplifier, and a detection system for deriving the video-frequencysignal. Goupled' in!v cascade with an output circuit of the unit =10,Lin` theordernamedpare a delay line 15, a luminancesignal amplifier- 16, a 0-3 `rnegacycle filter network 17, an adder circuit :13, and a single-gun image-reproducing apparatus 14. The delay line 15 is conventional and serves to equalize the time of translation of the luminance signal through the unit s 15, 16, and 17 with that for translation of .the chrominance signal through -other channels vtoQbe considered hereinafter. The amplier 16 is a conand a phase-adjusting circuit 32 to another input circuit of the axis selector 22. A control circuit inthe modulator 23 for controlling the conductivity thereof is .coupled to anoutput circuit of a color-killer circuit 36.in,the apparatus 12 and to be considered morefullyhereinafter. The ,output circuit of the generator 28Ais` also coupled through a phase-adjusting circuit 30 and a third harmonic amplifier 31 to an input circuit of the modulator 23. More complete consideration of the typeV of circuit ernployed for axis selection, such as represented by the G--M` axis selector 22will be ,given` when considering the apparatuslZindetail. Ingeneral, suchaxis selec- .tor isan amplierthe gain ofk which is periodically controlled in phase with a modulationcomponent of the subcarrier wavesignal soas toY translate such component with .high gain while not translating other components in quadrature therewithor translating suchwother components Withrelatively lowgain. lThe modulator 23, the filter network 24, and vthethird harmonic.,amplifierl ca nhe of conventional construction, unitsof these types being so well known as to require. no further description.` The phase-adjusting circuits 30 and 32 ar e net' worksfordelaying the phase of the signal generatedin the generator 28 lby appropriate amounts 'so that the signals applied to the axis selector 2 '2 and the modulator v2'3, after suchphas'e adjustments, are in phase with the desired modulation axis of thesubcarrier wave signal. In the circuit under consideration, siich axis is the G-M axis as more fully considered in the I. R. E. article last mentioned above.

There Vare also coupled in cascade in the order'named between an output eircuit of the amplifier 19 and an input circuit of the adder circuit 13, an M-Y synchronous detector 25 and a 0-0.6 megacycle filter network 26. An input circuit of the synchronous detector 25 is coupled to the color-killer circuit 36 to control the state of operation of the detector 25 in a manner to be considered more fully hereinafter. An additional input circuit of the synchronous detector 25 is coupled through a phase-adjusting circuit 33 to the output circuit of the generator 28 for the purpose of applying, from the unit 28 to the detector 25, a locally generated signal which is in phase with the M-Y modulation component of the subcarrier wave signal as more fully described in the aforesaid I. R. E. article.

A synchronizing-signal separator 37 is also coupled to an output circuit of the video-frequency signal source and has output circuits coupled through a line-scanning generator 38 and a field-scanning generator 39 to the horizontal and vertical deection windings 14e, respectively, in the image-reproducing apparatus 14. An output circuit of the generator 38, for example, a tap on the horizontal deection transformer therein is coupled to input circuits of the A. P. C. system 27 and the colorkiller circuit 36, both in the apparatus 12 and to be considered more fully hereinafter, for applying horizontal yback pulses as gating signals to such units.

An output circuit of the video-frequency signal source 10 is also applied to a sound-signal reproducing unit 40 which may comprise a conventional intermediate-frequency amplifier, an audio-frequency detector, an audiofrequency amplifier, and a sound reproducer.

Except for the details of combination of circuits in the 'video-frequency signal-translating apparatus 12, to be considered more fully hereinafter, all of the circuit components thus far described are conventional and well known, being fully considered in the January, 1954 VI. R. E. article entitled Processing of the NTSC Color Signal for One-Gun Sequential Color Displays. Therefore,.no detailed description of such circuit components is provided herein.

General operation of receiver of Fig. 1

Considering briefly now the operation of the receiver of Fig. 1 as a whole and assuming the apparatus 12 to be of a conventional type for developing a subcarrier wave signal modulated only by information representative of blue and red, that is, by an R*B component and is such as described in the aforesaid I. R. E. article, a desired composite color-television signal of the NTSC type is intercepted by the antenna system 11, selected,

amplified, converted to an intermediate-frequency signal,

further amplified, and the composite video-frequency signal component thereof detected in the unit 10. The composite video-frequency signal comprises conventional lineand field-synchronizing components, a color burst synchronizing component, and the aforementioned luminance and chrominance signals. The luminance signal is translated through the luminance-signal channel in- ,cluding units 15, 16, and 17 and through the adder circuit 13 and applied to the cathode of the image-reproducing apparatus 14. The chrominance signal is translated through the amplifier 19, converted in the apparatus 12 to a chrominance signal having only information representative of red and blue, that is, to a subcarrier wave signal modulated by an R-B component, and the converted signal, after translation through the filter network 21 and the adder circuit 13, is applied to the cathode of the picture tube in the image-reproducing apparatus 14. In the axis selector 22, the chrominance signal is converted to one including information representative of green, that is, to a subcarrier wave signal modulated by` a G-M component. In the modulator 23 such converted chrominance signal, having the same frequency as the initially applied chrominance signal, is heterodyned with a signal having the third harmonic frequency of the initially applied signal for developing a second harmonic amplifier 19 is also utilized in the synchronousdetector I 25 to derive a luminance-correction signal M-Y, the lowfrequency components of which are translated through the filter network 26 and the adder circuit 13 for utilization in 4the image-reproducing apparatus 14 to correct for luminance errors inherently caused by the chrominance signals in a single-gun tube such as utilized in the apparatus 14.

To effect proper operation of the axis selectors, such as the axis selector 22, and proper operation of the modulator 23 and the synchronous detector 25, that is, to control these units to operate in correct relationship with respect to the appropriate phases of the modulated subcarrier wave signal applied thereto, a sine-wave reference signal of the same frequency as the subcarrier wave signal is developed in the generator 28 and controlled in phase with respect to the subcarrier wave signal by means of the A. P. C. system 27. The system 27 is responsive to the reference signal and the color burst signal translated through the amplifier 19* and maintains the reference signal at a specific phase with respect to the color burst synchronizing signal and thus maintains the reference signal at specic phases with respect to the different modulation phases of the applied subcarrier wave signal. These phase relationships are represented by the vector diagram of Fig. la. The lll-B modulation axis of the subcarrier wave signal is 29 clockwise, the G-M axis 40 counterclockwise, and the M-Y signal 161 clockwise or 199 counterclockwise with respect to the phase of the color burst signal.

The reference signal developed in the generator 2S is doubled to a second harmonic signal in the amplifier 34 and the phase of such second harmonic signal is adjusted by means of circuit 35 so as to render the axis selector 20 conductive in phase with the R-B axis of the modulated subcarrier wave signal. The signal developed in the amplifier 34 is also adjusted in phase by means of the circuit 32 to cause the axis selector 22 to be conductive in phase with the GM phase of the applied subcarrier wave signal. The signal developed in the generator 28 is controlled in phase by the circuit 30 so as to have a specific phase with respect to the time of impingment of the beam in the picture tube on the green phosphors and such phase-controlled signal is then multiplied to a third harmonic signal in the amplifier 31, the latter signal being employed in the modulator 23 to develop a second harmonic subcarrier wave signal modulated by G-M information at a phase such that, when such developed signal is applied to the picture tube, the G-M information is applied to the green phosphors. The signal developed in the generator ZS is also controlled in phase by the circuit 33 to be in phase with the M-Y axis of the applied subcarrier wave signal, thereby to derive the N-Y component in the detector 25.

The signal developed in the generator 28 is also applied through the push-pull amplifier 29 to the `colorswitching grid 14b in the image-reproducing apparatus 14, the applied or color-switching signal having a specific phase relation to the fundamental subcarrier wave signal translated through the network 21, and which includes R-B information at a specific phase, and to the second harmonic subcarrier wave signal developed in the modulator 23, and which includes G-M color information at a specific phase. The phase relations of the color-switcm harmonic (S) ysubcarrier Wave signals.

ing, fundamentah'andsecond harmonicwave signals are as represented by the curves of Fig. l1b. AThe vertical lines G, R, R5 G, B, and B represent the tim'e's of impintg'# ment ofthe cathodearay beam on thefgreen (G), red (R), andblue (B) phosphors. Curve F represents thepha'se 'of the fundamental subcarrier wave signalmodulated by R-B information and it is apparent that the fundamental signal is in phase with the color-switching operation. Curve S represents the second harmonic subcarrier wave signal modulated by G-M information and curve Crep- Iesents the composite of the fundamental (fi) and second Line M reprepresents the corrected luminancesignal level, that is, the level for the signal M. In the synchronizing-signal separator 437, the lineand fieldfsynchronizing signals are separated from the com- .posite Video-frequency signal and from each other and are utilized, respectively, .in the generators 38 and 39 to develop horizontal deiiection and iield deflection signals employed in the deliection windings 14e to effect deflection of the cathode-ray beam toscan a raster on the image screen 14a. The scanning of such raster, the intensity modulation of the cathode-ray beam 'by means of the corrected luminance, fundamental subcarrier, and second harmonic subcarrier signals applied thereto, and the differential vertical deflection of the beam by .means -of the color-switching signal applied to the grid 14h combine to cause the intensity-modulated beam to impinge .upon `the phosphors for developing the different colors in correspondence with intensity modulation on such beamfor these colors, thereby to reproduce a color image.

In addition to the picture signal, a sound signal is also intercepted and an intermediate-frequency sound signal is derived from source 10. Such intermediate-frequency ysound signal is then further ampliiiedin the unit 40 and the audio-frequency components thereof are detected, 'adkditionally amplified, and utilized to reproduce sound in the unit 40.

When a monochrome television signal is intercepted by the antenna 11, all of the units in the receiver of Fig. l function in the manner just described except for some of the units used for developing color images. Since no color-synchronizing signal is received with a monochrome signal, the A. P. C. system 27 is unable to function and the ,color-switching signal developed by the generator 28, though it has a frequency of approximately 3.6 megacycles, is no longer locked in specific yphase relation with vline frequency. The failure of the A. P. C. system 27 to function causes the color-killer circuit 36, in a manner to be explained more fully hereinafter, to develop a negative bias potential which causes the modulator 23 and the detector 25 to become nonconductive and which changes the mode of operation of the selector 20 in a manner to be considered in detail. As a result, only monochrome information is applied to the picture tube to cause the reproduction of a monochrome image.

Description of video-frequency signal-.translating apparatus of Figs. 1 and 2 Inn describing the video-frequency signal-translating 'apparatus `of Fig. l, reference will be made to unit 12 yof |Fig. 1 to kdescribe generally the combination of specific vunits in accordance with the present invention and to Fig.

will reproduce color images when a color signal is received, monochrome images when a monochrome signal isbeing receivedyor a monochrome image at t-he :option of the viewer when a color signal .is being received. Als'o -as previously described herein, sch images 4are reproduced by excitation of a series of'groilps ofrphospho'r strips onV the image screen 14a fof the'd'evice 14, each group comprising strips in theseque'nce` green, red, green, blue. Consequently, the plurality of -primary colors yare the colors green, red, and blue and both the redand blue colors are developed at a rate within the frequency range of the "monochrome signal, that is, vat the colorswitching rete of approximately l3.6-megacycle's which is also the mean frequency of lthe modulated subcarrier wave signal.

The video-frequency signal-translating apparat-us.includes a circuit for supplyingthe high-frequency components of the monochrome or color signals, specifically an output circuit of the amplifier 19vfor-supplying signals having frequencies in therange of approximately megacycles. Thus, the supplied signal includes 'either high-frequency monochrome components in the range just mentioned or a subcarrier wave signal having a mean frequency of approximately 3.6 megacycles modulated over the range of 3.0-4.2 megacyeles.

-The video-frequency signal-translating apparatus also `includes signal-generating 'means for developing a-referspecifically, such generating means comprisesthe refervence-signal generator`28 for developing asignalwhich is substantially equal tol the mean frequency of the Amodulated subcarrier wave signal, that is, a signal ofy approxi- 4mately 3.6 megacy'cles and vmay include vthe second harmonic amplifier 34 coupled to the output 'circuit of the lgenerator 28.. vThe frequency of the signalldeveloped in the generator 28 is equal to, and the signal in the output circuit of the amplifier 34 twice, the period of development of either the red or blue colors in the imagereproducing device 14. These frequency relations are maintained by utilizing the signal ldeveloped in the generator 28, after translation through` the push-pull amplifier 29, on the color-switching grid '14h to effect the previously described color switching to cause the cathode-ray beam to trace a sinewave path centered on a green 'phosphor strip as it traces each horizontal line so that it impinges on the green, red, and blue phosphor strips, the sine-wave nature of the path causing the'beam to impinge on thevgreen'strips at twice the rate it impinges on the red and blue strips.

Referring to Fig. 2, the second harmonic amplifier 34 comprises a triode amplifier tube 50 having a cathode-grid input circuit 51 coupled to the output circuit of referencesignal generator 28 `and with the cathode grounded. The anode of the triode 50 includes a 'parallel-resonant circuit 52 coupled between a source of potential +B and the input'circuit of the phase-adjusting circuit 35. The parallel tuned circuit 52 is resonant at the second harmonicfrequency of the reference signal, thatis, at substantially v7.2 megacycles.

The video-frequency signal-translating apparatus 1K2 also includes phase-modifying means having a pairof selective phase-modifying conditions for causing the reference signal to have different phases with respect to the period of development of the aforementioned one color in different ones of the phase-1nodifying conditions. More specifically, such phase-modifying means comprises the phase-adjusting circuit 35 coupled between the output circuit of the amplifier 34 and an input circuit of the R-B axis selector 20. Y

Referring to Fig. 2, the phasee'adjustingcircuit 35 includes a triode amplifier 53 having the anode thereof coupled to a source of potential +B and the cathode coupled through a series-connected circuit of a biasing network 55 and a parallel tuned circuit 56 to the other terminal of the potential +B supply, that is, to ground. The tuned circuit 56 is resonant at approximately 7.2 megacycles. The control electrode of the triode 53 is coupled through a condenser 57, and the ungrounded terminal of the tuned circuit 56 is coupled through a condenser 59, to the resonant circuit 52 in the second harmonic amplifier 34. The control electrode of the tube 53 is also coupled through an isolating resistor 60 to the output circuit of the color-killer circuit 36 to be described in detail hereinafter.

The video-frequency signal-translating apparatus 12 also includes a control circuit coupled to the phasemodifying means for selecting different phase-modifying conditions thereof when color and monochrome images are being reproduced. More specifically, such control circuit comprises the automatic-phase-control system 27 and the color-killer circuit 36. The automatic-phasecontrol system 27 is of a type described in an article entitled The DC Quadricorrelator: A Two-Mode Synchronization System published in the January 1954 issue of the Proceedings of the I. R. E. at pages 288-299, inclusive. The details of such an automatic-phase-control system are particularly considered at page 293 of this article with reference to Fig. thereof. As described in such article, the system 27 includes the conventional quadrature-phase detector, for controlling the phase of the signal developed in the generator 28 so that the reference signal has a specific phase relation with respect to the modulated subcarrier wave signal, and also includes an in-phase detector. The in-phase detector is utilized to improve the automatic phase control of the system 27 and additionally develops a unidirectional potential which has a maximum magnitude when the signal developed in the generator 28 is in proper phase relation with respect to the modulated subcarrier wave signal. described in such article, such potential is negative when the generator 28 is properly synchronized. The colorkiller circuit 36 includes a triode amplifier 61 having the cathode thereof grounded and the control electrode thereof coupled to the output circuit of the in-phase detector in the system 27. The anode of the tube 61 is coupled through a secondary winding of a transformer 62, a low-pass filter circuit 63, and a manually operable switch 75 to the output circuit of the color-killer circuit 36. The primary Winding of the transformer 62 is coupled to the line-scanning generator 38, more specifically, to a tap on the horizontal deliection transformer in such generator at which a positive-going horizontal yback pulse is developed. A load resistor 64 is coupled between the cathode` and the anode circuits of the tube 61.

The video-frequency signal-translating apparatus 12 also includes a signal-translating device responsive to the aforementioned reference signal to have varying degrees of conductivity during each cycle of such reference signal. The signal-translating device is coupled to the supply circuit for effecting translation of segments of the supplied high-frequency components at the time of development of the one color, when a color image is being is being reproduced, and at times other than that of the development of the one color when a monochrome image is being reproduced. More specifically, such signal-translating device comprises the R-B axis selector 2t) including a pentode amplifier 65 having the controlgrid circuit thereof coupled through an isolating resistor 66 and a condenser 67, in series, to the cathode output circuit of the phase-adjusting circuit 35. The circuit just described is effective to apply the reference signal modified in frequency and phase by the units 34 and 35 to the control-electrode circuit of the tube 65 to vary the conductivity of the tube 65 cyclically at a 7.2 megacycle rate. The control electrode of the tube 65 is also coupled In the circuit .low visibility of any spurious patterns.

10 through the isolating resistor 66 and a coupling condenser 68 to the output circuit of the amplifier 19. The cathode circuit of the tube 65 is coupled through a biasing network 69 to ground while the anode of such tube is coupled through a load resistor 70 to a source of potential +B. T he suppressor electrode of the tube 65 is grounded while the screen electrode thereof is coupled through a load resistor 72 to the source of potential +B and through a `by-pass condenser 73 to ground. The anode output circuit of the tube 65 is coupled to the input circuit of the filter network 21.

Explanation of operation of vdeo-frequency signaltranslating apparatus of Figs. 1 and 2 Preliminary to considering the details of operation of the apparatus 12 of Fig. 1, it will be helpful once again to explain the purpose for such improved video-frequency signal-translating apparatus. As previously stated herein, the color-switching operation in the image-reproducing device 14 is effective to cause the cathode-ray beam developed in such device to impinge upon the different phosphors in a cyclic manner, specically, in the sequence green, red, green, blue for each group of phosphors. This operation occurs whether a color or monochrome image is being reproduced. When reproducing a color image, due to the previously described controlled phasing of the `color-switching and subcarrier wave signals, as represented hy the curves of Fig. lb, such cyclic operation is effective to cause the proper colors to be reproduced at the proper times. In addition, the interlaced relationship of the color information with line frequency results in However, when a monochrome image is being reproduced and the colors should be excited in such relative proportions as to reproduce shades of gray, there is no such interlacing due to the lack of synchronization between line frequency and the color-switching frequency and, consequently, the high-frequency monochrome information in the range of 3.0-4.2 megacycles tends to heterodyne with the 3.6 megacycle rate at which the colors red and blue are excited to cause spurious red and blue patterns to be developed. These spurious patterns represent beat signals in the range of 0-.6 megacycle being developed by the heterodyning of the 3.6 megacycle switching operation with the monochrome signals in the 3.0-4.2 megacycle range. Previously, in order to prevent such spurious patterns, monochrome information applied to the imagereproducing device 14 was limited to an upper frequency of 3 megacycles. v This solution Was wasteful of information and the improved video-frequency signal-translating apparatus 12 is utilized to modify the high-frequency monochrome information in the range of' 3.0-4.2 megacycles so that it may be usefully applied to the imagereproducing device 14. To effect this result, such information is applied only when the beam is impinging upon the phosphor for reproducing green, Since the color-switching frequency for reproducing green is twice that for reproducing red or blue, no visible spurious pattern occurs and high-definition monochrome information is reproduced.

To effect the above result, the R-B axis selector 20 which, when color is being reproduced, conventionally translates color components of the subcarrier wave signal which occur along the R-B phase axis, as represented in Fig. la, is controlled to translate information only when the electron beam is impinging on the green phosphors, when a monochrome image is being reproduced.

Since, under the latter condition, only the phosphor for '.Cuit `56 with-a phase `shift of substantially 90.

:l1 changed, so'that it will operate inthe manner just de- .'scribed, -by changing the phaseof the reference signal lapplied thereto. An axis selector is essentially an amplil-fier having gain which varies cyclically with the phase .ofthe information signal applied thereto, having maximum -'gain at specific phases or times of occurrence of lthe applied information, land minimum or no gain at l:phases in `quadrature with the specific phases or times. `By such variation in gain, the information at the specific phases or timesrof occurrence of the applied information signal is selected or translated through the axis selector while information at other times, corresponding to phases in quadrature with the specific phases of the information signal not selected, yis not translated through the axis selector `20, and is, therefore, rejected by the 'axis selector. Control .of the gain of the selector 24B is effected by employing a 7.2 megacycle signal properly adjusted in phase with respect to the color-switching signal to effect translation of the R-B modulation inforymation of the subcarrier Wave signal in coincidence with the impinging of'the cathode-ray beam on the red and blue phosphors, when a color image is being reproduced, and to effect translation of high-frequency monochrome Ainformation in coincidence with the impinging of the beam onthe green phosphors, when a monochrome image is being reproduced.

.Referring now to Fig. 2, the modulated sub-carrier wave signal is applied to the control electrode of the axis selector 20 through the condenser 68 and the isolating resistor 66. The signal developed in the generator 2S, controlled by the A. P. C. system 27 to have a specific phase with relation to the subcarrier wave signal, isheterodyned to a second harmonic signal in the arnplifier.34, adjusted.. in phase by the type of coupling between the circuits 52 and S6, and applied through the condenser 67 and the resistor66 tothe same control electrode of the amplifier 65. If the phase of the phase-adjusted reference signal is such as to have a positive peak iin p hase with the R-B phase axis of the applied sub- -carrler wave signal, in other words, to have positive peaks in coincidence with the exciting of the red and blue phos- :phors by the cathode-ray beam of the picture tube, then informationl along the R-B phase axis is translated through vthey tube 65, the filter network 21, the adder circuit 13, `and applied tothe cathode of the picture tube to excite the 4.redl and blue phosphors.

Information along quadraturephase axes, specifically along the axis in quadrature with the R-B. axis, is rejected by not being translated through the amplifier 65. If on the other hand, the phase of `the Vreferencefsignal applied-to the control electrode of `the tube 6S=is such as to have the positive peak thereof -in coincidence with the exciting of the green phosphors `'a color image is being reproduced, thereby causing the tube 53 to be conductive and to provide a low-impedance coupling between the tuned circuits 52 and S6 to provide substantially no phase shift for the 7.2 megacycle signal applied to the selector 20. The phase of the translated signal under such conditions is such as to cause axis selection along the R-'B axis in the manner previously discussed. When a monochrome image is being reproduced and a negative bias potential is applied to the grid circuit of the tube 53, the tube 53 becomes nonconductive. Consequently, the signal developed in the `output circuit of the amplifier 54 is coupled from the tuned circuit 52 through the condenser 59 to the resonant cir- Such phase-shifted signal causes'theaxis selector 20 tojtr'anslate information solely at times in coincidence with vthe excitation of the green phosphor by the cathode-ray beam in the image-reproducing device 14,

To summarize the above explanation, the axis selector 2f) is effective to translate information with respect to the red `and blue colors when a color image is b eing reproduced and to translate information only in coincidence with the excitation of the' green phosphors 'when a monochrome image is being reproduced. The phaseadjusting circuit 35 modifies the phase o f the second harmonic signal developed by the amplifier 3 4 so that it causes the axis selector to operate in the manner just described. The color-killer circuit 36 ldevelops the biasing potential for ythe phase-adjusting circuit 35 to control the phase-modifying conditions of s uch circuit.

'Lihe color-killer circuit v36 is describedatpage .293; of the January, 1954 I. R. E. and is simply an amplifier responsive to a positive-going yback pulse from the horizontal deflection transformer and the signal developed in the in-phase detector of the A. P. C. system 27. When the generator 28 is in synchronism with a color burst signal being received, a negative potential is applied by )to the triode 53 and causes it to become -nonconductive The switch -75 in the circuit coupling the 'anode of the tube 61 to the Icontrol electrode of the tube S3 permits the operator ofthe television receiver to effect monochrome reproductioneven when color information-is being received by applying the -C potential to the vtube 53 to cause. it to become nonconductive.

In considering .the above, it shouldbe understood that the improved video-frequency signal-translating apparatus is such as to cause high-frequency information in the range of l3.0-4.2 megacycles to be translated through a circuit and applied to the red and blue phosphors when a color image is being reproduced and corresponding information to be translated through the same circuit and applied only to the green phosphors when a monochrome image is being reproduced. The phosphors to which the translated information is applied are determined by the relative phasing of the color-switching signal controlling the beam position on the phosphors and the 7.2 megacycle reference signal applied to the axis selector. Consequently, the phase-modifying means described above may be employed either to modify the phase of the referencesignal with respect to that of the color-switching signal, in the manner just described, or, as will be described hereinafter with reference to Fig. 4, the phase of the color-switching signal may be modified with respect to that of the reference signal to accomplish the same purpose. Additionally, it should be recognized that the 'circuit for controlling the phase modification may automatically effect such modification not only when the applied signals differ, that is, are either color signals or monochrome signals, but also, at the option of the viewer, may effect such modification by means Vof the manual switch 75 so that a monochrome reproduction is obtainable even when the applied signals are color signals. Description and explanation of operation of video-frequency signal-translating apparatus of Fig. 3

ln the apparatus ll2 of Fig. l, the modified subcarrier wave signal modulated by the R-B component is translated through a channel parallel to the luminance channel. It is sometimes benecial to translate both the 13 luminance information and the subcarrier wave signal, modified to include R-B information, through the same channel. In addition, in the apparatus 12 of Fig. 1, separate phase-adjusting circuits and axis selectors are ernployed to obtain the R-B and G-M information. In the apparatus 312 of Fig. 3, a single axis selector of a composite type is utilized to effect selection of both the R-B and G-M information and a subcarrier wave signal, modified to include the R-B information or modified high-frequency components as previously discussed herein, is translated through the luminance channel with the luminance signal.

Since many of the units in the apparatus 312 of Fig. 3 are similar to units in Fig. l, such similar units are identified by the same reference numerals in both Figs. l and 3.

The apparatus 312 of Fig. 3 includes a composite axis selector 80. The axis selector 80 effects translation of G-M information through one path and R-B information through a different path when a color image is being reproduced and, when a monochrome image is being reproduced, effects translation of high-frequency information through the luminance channel only when the phosphors for developing green are being excited. The composite axis selector 80 includes a triode amplifier 81 having the anode thereof coupled through a parallel tuned circuit 82 to a source of potential +B and also coupled to a modulator such as the modulator 23 of Fig. 1. The cathode of the tube 81 is coupled through a seriesresonant circuit comprising an inductor 83 and a condenser 84 to the channel for translating the luminance signal, specifically, to an output circuit of the video-frequency signal source or to the input circuit of the delay line 15. The cathode is also coupled through an inductor 85 and a resistor S6 to the negative terminal of the B-potential source, specifically, to ground. Both the parallel- `resonant circuit 82 and the series-resonant circuit includpair of matrixing resistors 89 and 90 is connected in series between the anode of the tube 81 and the input circuit of the delay line 15, the junction of these resistors being connected to the M-Y synchronous detector 25 in the receiver of Fig. l. These resistors are proportioned to matrix the G-M and R-B components to provide an M-Y component. The vector diagram of Fig. la indicates the relationship of these components and the possibility of matrixing G-M and R-B to provide M-Y.

Except for the operation of the axis selector 80 and the translation of the subcarrier wave signal including the RB information through the same channel as the luminance signal, the video-frequency signal translating apparatus 312 of Fig. 3 operates in the same manner as the apparatus 12 of Figs. 1 and 2. The axis selector 80 is designed to make use of the fact that the R-B and G-M properly phasing the 7.2 megacycle signal applied to the control electrode of the triode 81, such triode can perform the function of the two axis selectors of Fig. l or 2 by translating the G-M components out of the circuit for translating the R-B components and leave only the R-B components in the latter circuit. More specifically, when a color image is being reproduced, the 7.2 megacycle signal applied to the control electrode of the triode 81 is adjusted in-phase to render the triode conductive at 14 the time when the G-M axis of the modulated subcarrier wave signal is applied to the cathode of the triode through the series-resonant circuit fait, 84. Since the triode is then conductive, it translates the information on the G-M axis to the anode of the triode and applies such to the modulator 23. At the time the R-B axis of the sub-carrier wave signal is applied to the cathode of the triode 81, the 7.2 megacycle signal is negative and the tube is not conductive. Therefore, the R-B information is retained in the channel for translating the luminance signal and, consequently, both the low-frequency luminance information, specifically, the 0-3 megacycle information and a subcarrier Wave signal having an upper side band extending to approximately 4.2 megacycles and modulated solely by R-B information are translated through the luminance channel.

When a monochrome image is being reproduced and only that information in the frequency range of 3.0-4.2 megacycles, which coincides in time with the time the electron beam is exciting the green phosphors, should be translated through the luminance channel, then the phasemodifying condition of the circuit 35 is changed in the manner previously described herein to cause the action of the triode 81 to effect such result. Specifically, when a monochrome image is being reproduced, the triode 81 becomes conductive at the times the electron beam in the picture tube is impinging on the red and blue phosphors, thereby shunting any high-frequency information occurring at such times out of the luminance channel, and, consequently, no high-frequency information is applied to such phosphors. The triode 81 is rendered nonconductive during the times the beam in the cathode-ray tube is impinging on the green phosphors and, therefore, al1 of the high-frequency monochrome information occurring at the latter times remains in the luminance channel and is applied to the green phosphors.

Description and explanation of operation of Fig. 4

As stated previously, in accordance with the present invention, the phase of the reference signal applied to the R-B axis selector may be modified to effect the results described above when reproducing color and monochrome images or the reference signal may remain unmodified and, therefore, the operation of the R-lB axis selector remains unmodied while the phase of the color-switching signal is modified with respect to the reference signal. The same results are obtained by either modifying the phase of the reference signal with respect to the colorswitching signal or by modifying the phase of the colorswitching signal with respect to the reference signal. The video-frequency signal-translating apparatus of Fig. 4 represents apparatus in which the latter phase modification is effected.

Since in the apparatus 412 of Fig. 4 many of the units are similar to units in Fig. l, the same reference numerals are used for such units in both Figs. 1 and 4. In Fig. 4, a phase-adjusting circuit 92 having constant phasemodifying characteristics is coupled between the output circuit of the second harmonic amplifier 34 and an input circuit of the R-B axis selector 20. A phase-adjusting circuit 93 having different phase-adjusting characteristics when monochrome and color images are being reproduced is coupled between the output circuit of the referenceslgnal generator 28 and the input circuit of the pushpull amplifier 29. The phase-modifying conditions of the circuit 93 are controlled by the signal developed in the color-killer circuit 36 in the manner previously described herein with reference to the phase-adjusting circuit 35 of Fig. l.

The operation of the apparatus 412 of Fig. 4 differs from the apparatus 12 of Fig. l solely in that the phase of the color-switching signal is modified instead of modifying the phase of the reference signal applied to the axis selector 20. The same results are obtained in either case. The phase-adjusting circuit 93 is controlled to cause the ,color-.switching signal t9 havens@ Phase .with ,respect to the subcarrier Wave signal translated through A thejaxis selector when a colorl image is being reproduced, specifically to have such phase that the subcarrier ,wave signal translated through the axis selector 20 applies red and blueinformation to the properphosphors. When a monochrome yimage is being reproduced, the phasey of the color-switching `signal is modified, in the vmanner previously des c r ibed herein, to cause the signal translated through t h e ax is selector 2Q to apply information solely to the 1 phosphors vvfor reproducing green. In this way, tlie spurious red and b lue patterns in reproduced. mndchrome imagens@ minimized While `there have been described v vh'at are at present lgrnsideredfo be thepreferred embodiments of this invention, it will be obvious tothosefslsilled in the art that various changes andmodilicationsmay be made therein without departing from theinvention, and it is, therefore, Aaimedpto cover allmsuchschanges and modifications as fall within thetruevspirit and scope ofthe invention.

Whatisslaimsdiss-...m-.a

1, :In a compatible image-reprodueingsy'stem including means for reproducinga monochrome or color image by periodic sampling of different primary color elements and susceptible vto spurious color distortions during the reproduction of amonochrome image due to sampling of high-frequency video components upon their application no elernents' o f a given primary color, video-frequency signal-translating apparatus eomprising: a circuit for supplying atleast the highffreqnency components vof said Amonochrome or color signals; lsignal-'generating means for developing a reference signal harinonicallyv related in frequencytothesampling rate of elements of said given color and having different phases with respect to the sampling timesnof said given c olor when `color and monochrome images are.,beingreproduced; and signal-translating means coupled to'said signal-generating means and having a varying sig'nal-translationfactor controlled by said reference signalvand ycoupled to said supply circuit for effecting translationof said supplied high-frequency components primarily at said sampling times of said given rcolor when a color image is being reproduced and pri- -marily at other times when a monochrome image is being reproduced.

2. In a compatible image-reproducing'system including means for reproducing amonochrome or color image by periodic'sampling ofdtferent primary color elements and susceptible to spurious color distortions during the reproduction of a monochrome image due to sampling of 'high-frequency video components upon their applica- Cal tion to elements of a given primary color, video-frequency signal-translating apparatus comprising: a circuit for supplying the high-frequency components of said monochrome or color signals; signal-generating means for developing a referencey signal having twice the frequency of the sampling rate of elements of said 'given color and having diferent phases with respect tothe sampling times of said given co-lor when color and monochrome images are being reproduced; and signal-translating means `coupled to said signal-generating means and having a varying signal-translation factor controlled by said reference signal and coupled to said supply circuit for efecting translation of said supplied high-frequency components primarily at said sampling times of said given color when a color image is being reproduced and primarily at other times when a monochrome image is being reproduced. v

3. In a compatible image-reproducing system including means for reproducing a monochrome or color image by periodic sampling of green, red, and blue color elements and susceptible to spurious color distortions during the reproduction of a vmonochrome image due to sampling'of high-frequency video components upon their application to elements o f said red and blue colors, video-frequency signal-translating apparatus comprising:

a circuit fof supplying the high-frequency components of said monochrome rcolor signals; 'signal-generating means for developing a L'reference signal harmonically related in frequency to the individual sampling rates of elements of said'red and blue colors and having different phases with respect to the sampling times of said red and blue colors when color and monochrome images are being reproduced; and signal-translating means coupled to said signal-generating means and having a varying lsignal-translation factor controlled by said refer ence "signal to have varying degrees o f conductivity during each cycle thereof and coupled to said supply circuit for effecting translation of said supplied high-frequency components of said red and blue colors when a color image isv being reproduced 'and primarily at `sampling the time of said green colorwle'na'monochrome image is being reproduced. a

4. Video-frequency 'signal-'translating apparatus for acompatibleimageLreproducing vsystem for reproducing, in response to applied monochrome `or color signals, y:a monochrome or :color image, respectively, from `'a 'plurality of primary colors developed Yin sequence at least one of lwhich is periodically developed at a rate within the frequency range of 'the monochrome signal and anotherfof vvhich is periodically developed at twice-'said rate, comprising: 'a circuit for'supplying the high-frequency components ofsaidmonochromeor color signals;

-'signal-generating 'means for developing a reference' signal equal in frequency t'o said period of 'development :of said other color; for causing said `refer'ence signal to have different phases "withlr'espect ltosaid period when color and monochrome images "are"being `reproduced; and

signal-translating means 'responsive to "saidsreference sig- "nal to'ha'v'e 'tw'o periods of"conductivityduringeachV of said s'equencesand coupled to" saidsupply circuit for effecting translationof segments ofsaid"supplied high-frequency components lprimarily at the .time of development of said one color whena color image is being reproduced and primarily at the time of development of said other 4color` when am'onochrome image is -being reproduced.

5. Videofreq'u'ency signal-translating apparatusv for --a compatible" imagereproducing system for reproducing, in response to applied monochromev or color signals, a monochrome or color image, respective, from a plurality of primary colors at 'least onef of ,whichl is periodically developed at'approximately a 3:6 megacycle rate, comprising:` a 'circuit for supplyingsubstantially the 3.0-4.2 megacycle components of 'said monochrome'4 or color signals; signal-generating'r'neans for developing a r'eferencesignal of approximately '7.2 megac'ycles; means for causing said reference signal to have different phases with respect to said period when coloran'dmonochrome images are being reproduced; and signal-translating means responsive to said reference' signal yto 'haveperiods of maximum conductivity ata 7L2 megacycle rate and coupled to said supply circuit for 'eecting translation of segments of said 3.0-4.2 megacycle components primarily at the time 'of development of"said`one color'whe'na color image is being reproduced and primarily attimes other than that of the development of said one color when a monochrome image is being reproduced.

6. Video-frequency lsignal-translating apparatus for a compatible image-reproducing s'yst'emfor reproducing, in response to applied monochrome or color signals, a monochrome'or color image, respectively, from a plurality of primary lcolors atleast one of lwhich'ispe'riodically develope'drat a rate approximating the frequency range of the monochrome signal, `col-uprising: a circuit for supplying the highfrequency 'components "of `said monochrome or color signals; signalgeneratiiig Emeans for ldeveloping a reference signal harmonicallyfrelated in frequency to said period of development'of said one color; means for translating "said reference signal with different phases with respect "to Said 'period When color and'monochromeimag'es are being eprodue'and sig- 17 nal-translating means coupled to said phase-modifying means and responsive to saidtranslated reference signal to have varying degrees of conductivity during each cycle thereof and coupled to said supply circuit for eiecting translation of segments of said supplied highfrequency components primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

7. Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from a plurality of primary colors at least one of which is periodically developed at a rate approximating-the frequency range of the monochrome signal, comprising: a circuit for supplying the high-frequency components of saidmonochrome or color signals; signal-generating means for developing a reference signal for controlling said period of development of said one color and harmonically 'related in frequency thereto; means coupled to said signalgenerating means for translating said reference signal with different phase delays for causing the time of development of said one color to change with respect to a reference phase of said generated reference signal when color and monochrome images are being reproduced; and signal-translating means coupled to said generating means and responsive to said reference signal developed therein to have varying degrees of conductivity during each cycle thereof and coupled to said supply circuit for effecting translation of segments of said supplied highfrequency components primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

8. Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from a plurality of primary colors at least one of which is periodically developed at a rate approximately the frequency range of the monochrome signal, comprising: a circuit for `supplying the high-frequency components of said monochrome or color signals; signal-generating means for developing a reference signal harmonically related in frequency to said period of development of said one color; an electrondischarge device having a pair of coupled resonant circuits tuned to the frequency of said reference signal for translating said reference signal with dilferent phase delays when said device is conductive and nonconductive; a control circuit coupled to said electron-discharge device for causing said device to have different states of conductivity when color and monochrome images are being reproduced; and signal-translating means responsive to said reference signal to have varying degrees of conductivity during each cycle thereof and coupled to said supply circuit for etecting translation of segments of said supplied high-frequency components primarily at the time of development of said one color when a color image is beingreproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

9. Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from a plurality of primary colors at least one of which is periodically developed at a rate approximately the frequency range of the monochrome signal, comprising: a circuit for supplying the high-frequency components of said monochrome or color signals; signal-generating means for developing a reference signal harmonically related in frequency to said period of development of said one color;

phase-modifying means for causing said reference signal to have different phases with respect to said period; a signal-identiiication circuit coupled to said. supply circuit and said phase-modifying means for identifying said supplied components as monochrome or color and for altering the operation of said phase-modifying means when color and monochrome images are being reproduced; and signal-translating means responsive to said reference signal to have varying degrees of conductivity during each cycle thereof and coupled to said supply circuit for etecting translation of segments olf said supplied high-frequency components primarily at the timeof de` velopment of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

l0. Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from a plurality of primary colors at least one of which is periodically developed at a rate approximating the frequency range of the monochrome signal, comprising: a circuit for supplying the high-frequency components of said monochrome or color signals; signal-generating means for developing a reference signal harmonically related in frequency to said period of development of said one4 colo-r; an electron-discharge device having a pair of coupled resonant circuits tuned t-o the frequency of said reference signal for translating said reference signal with one phase delay when said device is in one conduction condition and with another phase delay when said device is in another conduction condition; a control circuit responsive to said supplied components for developing an identification signal identifying said components as monochrome or color and coupled to said device for utilizing said identification signal to cause said device to have said one conduction condition when color images are being reproduced and said other conduction condition when monochrome images are being reproduced; and signal-translating means responsive to said phase-delayed reference signal to have varying degrees of conductivity during each cycle thereof and coupled to said supply circuit for effecting translation of segments of said supplied high-frequency components primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

, 11. Video-frequency signal-translating apparatus for a I compatible image-reproducing system for reproducing, in.

means for causing said reference signal to have different phases with respect to said period when color and monochrome images are being reproduced; and a periodically conductive device having lthe conductivity thereof periodically controlled by said reference signal and coupled to said supply circuit for effecting translation `of segments of said supplied high-frequency components primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

12. Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing,

lin response to applied monochrome or color signals, a

19 monochrome or color image, respectively, from a pluralityof primary colors at least one of which is periodically developed at a rate approximately the frequency range of the monochrome signal, comprising: a signal-translating channel for translating said monochrome or color signals; signal-generating means for developing a reference signal harmo-nically related in frequency to said period of development of said one color; means for causing said reference signal to have different phases with respect to said period when color and monochrome images are being reproduced; and signal-translating means responsive to said reference signal to have Varying degrees of conductivity during each cycle thereof and having an input circuit coupled to said signal-translating channel and having one output circuit for effecting translation of segments of the high-frequency components of said mono-chrome or color signals primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced and having an output circuit for translating the segments of said high-frequency components yof said monochrome or color signals untranslated by said one output circuit when said color image is being reproduced.

13. Video-'frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from a plurality of primary colors at least one of which is periodically developed at approximately a 3.6 megacycle rate, comprising: a circuit for supplying substantially the 3.0-4.2 megacycle components of said monochrome or color signals; signal-generating means for developing a reference signal having a frequency of approximately 7.2 megacycles; for causing said reference signal to have different phases with respect to said period when color and monochrome images are being reproduced; and a periodically conductive amplifier responsive to said reference signal and rendered conductive thereby at approximately a 7.2 megacycle rate and coupled to said supply circuit for effecting translation of segments of said 3.0- 4.2 megacycle components primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that Of the development of said one color when a monochrome image is being reproduced.

14. Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from green, red, and `blue primary colors, the red and blue colors being periodically developed at a 3.6 megacycle rate and the green at a 7.2 megacycle rate, comprising: a circuit for supplying substantially the 3.0-4.2 megacycle components of said monochrome or color signals; signal-generating means for developing a reference signal of approximately 7 .2 megacycles having a specific phase with respect to said 3.6 megacycle rate; phase-modifying means for translating said reference signal with different phases with respect to said 3.6 megacycle rate; a signal-identification circuit coupled to said supply circuit and said phase-modifying means for identifying said supplied components as monochrome or color and for altering the operation of said phase-modifying means when color and monochrome images are being reproduced; and a periodically conductive amplifier responsive to said translated reference signal and rendered conductive thereby at a 7.2 megacycle rate and coupled to said supply circuit for effecting trans'- lation of segments of said suppliedA 3.0-4.2 megacycle components primarily at the times of development of said red and blue colors when a color image is being reproduced and primarily at the time of development of said green color when a monochrome image is being reproduced.

CTL

15. Video-frequency signal-translatingapparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from a plurality of primary colors at least one of which is periodically developed at a rate approximately the frequency range of the monochrome signal, comprising: a circuit for supplying the high-frequency components of said monochrome or color signals; signal-generating means for developing a reference signal harmonically related in frequency to said period of development of said `one color; an electron-discharge device having a pair of coupled resonant circuits tuned to the frequency of said reference signal for translating said reference signal with one phase delay when said device is conductive and with a longer phase delay when said device is non-conductive; a control circuit responsive to said supplied components for developing an identification signal identifying said components as monochrome or color and coupled to said device for utilizing said identification signal to cause said device to be conductive when color images are being reproduced and non-conductive when monochrome images are being reproduced; and a periodically conductive amplifier responsive to said phase-delayed reference signal and cylically rendered conductive thereby and coupled to said supply circuit for effecting translation of segments of said supplied high-frequency components primarily at the time of development of said one color when a color image is being reproduced and primarily at times other than that of the development of said one color when a monochrome image is being reproduced.

16.V Video-frequency signal-translating apparatus for a compatible image-reproducing system for reproducing, in response to applied monochrome or color signals, a monochrome or color image, respectively, from green, red, and blue primary colors, the red and blue colors being periodically developed at substantially at 3.6 megacycle rate and the green at substantially a '/.2 megacycle rate, comprising; a circuit for supplying substantially the 3.0-4.2 megacycle components of said monochrome or color signals; signal-generating means for developing a reference signal of approximately 7.2 mega-cycles having a specific phase with respect to said 3.6 megacycle rate; an electron-discharge device having a pair of coupled resonant circuits tuned approximately to 7.2 megacycles for translating said reference signal with one phase delay when said device is conductive and with a quadrature-phase delay when said device is nonconductive; a signal-identification circuit responsive to said supplied components for developing an identification signal identifying said components as monochrome or color and coupled to 'said device for utilizing said identification signal to cause said device to be conductive when color images are being reproduced and nonconductive when mono-chrome images are being reproduced; and a periodically conductive amplifier responsive to said phase-delayed reference signal and rendered conductive thereby at substantially a 7.2 megacycle rate and coupled to said supply circuit for effecting translation of segments of said supplied 3.0-4.2 megacycle components primarily at the times of development of said red and blue colo-rs when a color image is being reproduced and primarily at the time of development of said green color when a monochrome image is being reproduced.

17. Video-frequency signal-translating apparatus for a compatible television system comprising: a color tube in which color or monochrome images may be produced by periodic switching to different primary colors, the tube being subject to undesirable color effects when displaying in monochrome because of heterodyning between the switching signals and high-frequency video signals; means for supplying the video information representative of those high-frequency video signals to said tube in proper phase to be switched by the switching signals to the different primary colors when displaying a color image; and means for supplying to said tube only that part of the video infomation representative of those high-frequency OTHER RFERENCES Viqeo Signals corespopdingto the timing of o. of said Color TV, Rider Pub., March 1954, pagos 141 and 142. Primary colors when dlsplaymg a monochrome Image' Introduction to Color Television, Admiral Corporation,

References Cited in the file of this patent 5 February 1954 pages 17 to 27' UNITED STATES PATENTS i 2,744,952 Lawrence May 8, 1956 2,745,899 Maher May 15, 1956 UNITED STATES PATENT OFFICE CERTIFICATE OF 'COBRECTIGN Patent No., 2,856,454 Gctober 1.4, 1958 Bernard D., Loughlin It is hereby certified that error appears in the -printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 16, line 14, after "components'l insert primarily at said sampling times line l5, after "at" insert m the n; line 16, before "time" strike out "the"; line 30, before "for" insert means column 16, line 44, for "respective" read M- respectively M; column 1'7, lines 43 and '70, and column 19, line 3, for "approximately", in each occurrence, read approximating m; column 19, line 36, before "for" insert means column 20, line 6, for 'Yapproximately'l read approximating line 37, for "at", second occurrence, read a Signed and sealed this 24th day of February 1959.

(SEAL) Attest:

KARL H AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

